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28 Cards in this Set
- Front
- Back
What are the vitamers of Vit E and how do their structures differ?
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a-b-g-d tocopherol.
Two rings. Important on is conjugated & with one OH and multiple CH3 groups. a = 3 CH3 B, g = two d = one activity roughly correlates to # of CH3 groups |
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What is a free radical?
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A compound that can exist independently that has one or more unpaired electrons
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What are some examples of free radicals?
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O2!
Superoxide RO - alkolyl ROO - peroxyl OH - hydroxy |
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How is a lipid peroxide formed?
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LH --> L• + H
L• + O2 --> LOO• |
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What initiates lipid oxidation?
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OH•, RO•, ROO• : a number of free radicals
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Where do initiators come from?
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OH• : gamma ray fission of H20
and indirectly from LOOH and superoxide |
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Draw the cycle of oxidation!
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See book
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What is a hydroperoxide?
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LOOH (or ROOH)
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What (in words) is the Haber-Weiss rxn? What is required?
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The pathway that forms a hydroxy radical (OH•) from a hydroperoxide (ROOH)
Catalyzed by Fe2+ Requires superoxide |
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Write the Haber-Weiss reaction
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ROOH + O2-• ---> OH• + RO- + O2
(Fe) |
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How does Vit E terminate the chain reaction?
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OH group reacts w/ROO•
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Why is Vit E stable?
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Conjugated ring: unpaired electron is delocalized throughout ring structure; more stable, less reactive arrangement.
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How is Vit E regenerated?
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It is regenerated from ascorbate. H gets donated. Ascorbate --> semi dehydro ascorbate. (Which then reacts w/itself "disproportionation")
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What is the term called when Vit C regenerates Vit E?
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Quenching
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What is Malonaldehyde? Why is it so bad?
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A bi-product of lipid oxidation. O=CH-CH2-CH=O
Two aldehyde groups are very reactive with free amines; crosslinking (polymerization) can occur. |
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Why do we care about lipid peroxides anyways?
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Lipids are in membranes.
• disruption of hydrophobic nature of membranes "fragmentation" • loss of membrane bound enzyme activity • formation of aldehyde/ketone groups ie malonaldehyde |
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Lipid (hydro)peroxides are being formed all the time by us; How are they then metabolized? (1st rxn & enzyme)
(LOOH) |
(1) RXN with glutathione (GSH):
LOOH + 2GSH --> LOH + GSSG +H2O forms lipid alcohol (b-ox) Enzyme = glutathione peroxidase Co-factor = Se!!! |
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How does adequate Se reduce the load of Vit E required?
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LOOH can go either the route of Haber-Weiss and form additional free radicals, or it can be metabolized via Se-requiring pathway. If added free radicals, more Vit E required to quench.
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What is GSSG?
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Oxidized glutathione (GSH)
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What happens to GSSG created during LOOH metabolism?
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It gets regenerated (reduced) back:
GSSG + NADPH+H --> 2 GSH + NADP Enzyme: glutathion reductase Co-factor: RF |
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What is glutathione? (What is it made of)?
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Tripeptide containing cysteine (sulfur group).
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Se is known to ameliorate need for Vit E. Sulfur amino acids do too. Why?
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LOOH + 2GSH --->
GSH: sulfur-containing tri-peptide (cysteinyl). |
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Draw the "unified anti-oxidant action" schematic- for the fate of LOOH
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Draw it; see notes.
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What causes most Vit E deficiencies?
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Fat malabsorption from disease.
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Signs of Vit E def?
Susceptible populations? |
Signs include spinal cord degeneration, swollen axons, accumulation of organelles.
Susceptible population: premies |
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What deficiency sign is found in premies?
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Hemolytic anemia. It's a decrease in RBC survival without increased production - premature lysis.
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Vit E Biochemical method of assesment?
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Most common: plasma or blood serum a-tocopherol status
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Function test of Vit E status?
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Two main ones:
Erythrocyte hemolysis in vitro when exposed to H202 - measure time to lysis and Breathe ethane & pentane (which are FA ox products) |